In U.S. Pat. No. 3,274,209 there are described 6-aryl-2,3,5,6-tetrahydroimidazo[2,1-b]thiazole derivatives as anthelmintics. The use of 2,3,5,6-tetrahydro-6-phenylimidazo[2,1-b]thiazole in aiding the regression of neoplastic disease is described in U.S. Pat. No. 4,584,305. The immunostimulating properties of (S)-(-)-2,3,5,6-tetrahydro-6-phenylimidazo[2,1-b]thiazole, generically known as levamisole, were described in Immunopharmacology 1, 245-254 (1979), Clin. exp. Immunol., 22, 486-492 (1975) and the references cited therein. The compound 5,6-dihydro-3,5,6-triphenylimidazo[2,1-b]thiazole is described in Gazz. Chim. Ital., 114, 201-204 (1984) [CA; 101: 211027f] and the compound 5,6-dihydro-6-phenylimidazo[2,1-b]thiazole-3-acetic acid ethyl ester, dihydrochloride in J. Heterocycl. Chem., 19, 343-348 (1982). Neither compound appears to have any useful pharmacological or other properties.
The compounds of the present invention differ from the prior art by the fact that the 2,3-bond is unsaturated and that either the 2 and/or the 3-position are substituted. Further, the present compounds are unexpectedly far more potent immunostimulating drugs than the prior-art compound levamisole.
2-Hexyl-5,6-dihydro-6-phenylimidazo[2,1-b]thiazole oxalate has been described in Acta Antwerpiensia, 1991, 8 (2), 37-46 and in the International Journal of Immunopharmacology, 1991, 13 (6), 764.